A hailstorm is a weather event in which hail falls abundantly, typically during severe thunderstorms with updrafts powerful enough to keep ice stones suspended in the cloud while they accumulate successive layers of ice. Hailstorms can produce stones from a few millimetres to over 10 cm in diameter (grapefruit-sized), with fall velocities reaching 150 km/h. Southern Europe is one of the regions most affected by severe hailstorms, especially in river valleys, plains, and Mediterranean coasts during spring and summer. Hailstorms associated with supercells or squall lines can devastate crops in minutes, causing multi-million losses to fruit campaigns nearly every summer. Autumn DANAs across the Mediterranean also generate large hail. Protection against hailstorms includes: hail nets (widely used in fruit-growing regions), agricultural insurance, weather radars with hail detection algorithms, and the controversial anti-hail cannons and cloud seeding with silver iodide (whose effectiveness is not conclusively proven scientifically). Weather models and atmospheric soundings are the main tools for predicting hail risk through indices such as CAPE and vertical wind shear.